The present invention relates to systems for monitoring the movement of objects through a predetermined path. The invention is particularly suited, and is therefore described below, for use in monitoring the rate of feed of a seed feeding device for assuring that the seeds are fed according to a predetermined minimum rate.
Seed planters usually include a plurality of seed feeding devices, one for each row being planted. Such planters are frequently used for seeding corn, soya beans, cotton, beets and the like. The yield of these and other crops can be increased by assuring that each row of the planter is continuously working, and that each row is dropping the seeds according to a predetermined minimum rate.
One type of seed monitoring system heretofore used includes mechanical switches which are actuated as a result of physical contact with the seeds, an example of such a system being described in U.S. Pat. No. 2,907,015. Other seed sensing devices have also been used, such as optical sensors as described in U.S. Pat. No. 3,537,091.
In the foregoing types of systems, the indicator is usually in the form of a lamp which is flashed each time a seed is sensed. This means that the operator must continuously watch the lamp and its rate of flashing to see whether the seeds are being fed and at what rate. Such arrangements, however, are very awkward to monitor particularly when a large number of rows of seeds are being planted simultaneously, since the tractor driver must, among his other functions, continuously watch all the lamps to make sure they are flashing at the proper rate.